Aerator



' E. c. LATHROP ET'AL Feb. l5, i949.

AERATOR 2 Sheets-Sheet-l Filed Jan.` 15, 1946 SMQ/WIM@ E.C.LTHROP S.H.ARONOVSKY Feb 15, 1949- v E. c. LATHROP ET Al. ALMS AERTOR Fi1 ed Jan. l5, 1946 2 Sheets-Sheet 2 ,LTH HOP .ARGNOVSY Patented Feb. 15, y1949 Elbert C. Lathrop AERATOR and Samuel I. Aronovsky, Pe-

oria, Ill., assignors to the United States of America as represented by the Secretary of Agriculture Application January 15, 1946, Serial No. 641,357

(Cl. 259-43) (Granted under the act of March 3, 1883, as

1 Claim.

This application is made under the act of March 3, 1883, as amended by the act of April 30, 1928, and the invention herein described and claimed, if patented, may be manufactured and used by or for the Government of the United Statesv of America for governmental purposes without the payment to us of any royalty thereon.

This invention relates to an apparatus for incorporating into viscous materials finely divided air cells and is more particularly concerned with incorporation of air cells which are microscopic in size. In co-pending applications Serial No. 499,508 (Pat. No. 2,433,849) and Serial No. 503,002 (Pat. No. 247,699), led August 21, 1943, and September 18, 1943, respectively, there are disclosed methods of preparing plastic compositions of matter for use as cork substitutes. In the course of preparing such compositions of matter, an aqueous mixture of a proteinaceous material, a plasticizer therefor, and finely divided particles of a, pithy substance are mixed together. This composition is viscous and usually has a density of about 1.12 to 1.14. This material is then subjected to aeration for the purpose of incorporating therein a, suicient quantity of air inthe form of microscopie air cells similar to those found in natural cork. The air is usually incorporated in this composition in an amount to reduce the density to about 0.6 to 0.8.

We have found that when small batches of the viscous material are used, it is not difficult to incorporate the required amount of air in the form of microscopic cells. For example, quantities of about 600 cc. are not diiiicult to handle for this purpose using commercially available devices, such as ordinary kitchen food mixers. However, when larger quantities of the material are to be aerated, such devices are not satisfactory. They are deficient to the extent that the necessary amount of air cannot be introduced or, if introduced, a large number of air cells are above microscopic size. Such conditions make it impossible to manufacture a proper-cork substitute since the larger air cells weaken the structural strength of the final product at the points where they may exist. cannot be used, for example, in fabricating crown seal discs and gaskets since the presence of large cells of air, by weakening the structural strength, will tend to produce leakage under pressure, especially under the pressures usually employed in carbonated beverages and the like.

Although it is possible to use conventional apparatus for preparing satisfactory compositions of matter in accordance with the inventions referred to, such apparatus can only be used on a small scale, such as is indicated above. Such small scale production, however, is impractical for commercial purposes where it is necessary t0 amended April 30, 1928; 370 0. G. 757) make large quantities of the material. Accordingly, it is the object of this invention to provide an apparatus which can be used to incorporate in a liquid composition ofthe type mentioned the required amount of air in the form of microscopic air cells for commercial uses.

It is a further object of this invention to pro vide apparatus of the type mentioned which will permit the carrying out of the aeration process in a continuous manner.

A still further object of this invention is to provide an apparatus of the type mentioned which is very rapid in its operation.

We have found that, in order to obtain the required type of aeration, it is necessary that the material to be aerated be so agitated in a container as tov provide a deep, wide vortex just above the impeller blades used to agitate and circulate the material. We have also found that it is necssary for the apparatus to be so arranged that the material is circulated in a vertical path upward along the sides of the container and then permitted to cascade downwardly into the vortex in a plurality of folds. This action prevents violent agitation of the material at surfaces that are in contact with outside air and results in the incorporation of the desired micro- Material of4 this kind y scopic air cells without occlusion of the undesirable large air cells.

Inthe accompanying drawing, there is illustrated a preferred embodiment of this invention whichl incorporates the principles described In the drawing:

Figure 1 is a sectional view in elevation of a preferred embodiment of this invention.

Figure 2 is a plan view of the embodiment illustrated in Figure 1, partly broken away.

Figure 3 is anotherplan View similar to Figure 2 showing the pattern of the material While being aerated.

Figure 4 is a diagrammatic elevational View of a plurality of the devices illustrated in the previous gures, showing how they maybe arranged in series to provide a continuous operation.

Referring withmore particularity to the drawing in which like numerals designate like parts, the numeral II designates a cylindrical container which may be of any desired size. Within the container, there is disposed a partition member or sleeve l2 which may be in the form of an inverted hollow truncated cone, supported above the bottom of the container by means of spaced legs I3. The lower portion of the member l2 is imperforate, while th upper portion is slotted to provide a plurality of weirs I4. The strips l5 divide the weirs I4, extend to the top of the container Il, and are secured to the top by any suitable means such as by crimping over the edge. At intervals, bolts I6 may be used to provide aV more secure seating.

At the bottom of the member I2, there is diswhich upon rotation will cause liquid material above it to be forced downward. The impeller I1 is secured to the bottom of a vertical shaft I8 which extends upward and is connected to the power take-off of a motor I9 operating preferably at a speed of 1800 R. P. M. or more. In order to avoid vibration, the motor is supported independently of the container as shown.

On one side of container Il, there is provided posed an impeller blade I1, having a contour an opening communicating with a downwardly sloping trough 2|. On the inside of container II, adjacent the opening 20, there is disposed a slidable gate 22 in vertical guides 23, which may be secured in different vertical positions to adjust the maximum height of liquid in the con- -tainer and thereby vary thel overflow of the streams descend, they converge, enfold air, and

finally merge at the center of the vortex where they are pulled into the mass below the impeller, whereupon the cycle is repeated. This action is characteristically gentle and devoid of violence along the surfaces of the material which at any particular instance may be exposed to the atmosphere. This avoids the occlusion of undesirable large bubbles or air.

As this action is maintained and air becomes incorporated in the liquid, the density of the material decreases and the volume increases. This increase in volume has the effect of increasing the height of the vortex above the plane of the impeller` blade I1. The greater this height the less efficient is the aeration.` In order to maintain the eiciency which is obtained by a low vortex, it is necessary to discharge some of the material from the container. This is accomplished by adjusting the height of the gate 22 to obtain an overflow of the excess material until a proper level of the vortex is obtained. In operating the apparatus in a batch process, the overflow material is collected for incorporation in subsequent batches. The material remaining in the device is continued to be agitated until a predetermined density is obtained. s

In order to avoid inefficiency resulting from the removal of partly aerated material as described above in the batch process, a series of such apparatus may be arranged, such as illustrated in Figure 4, whereby the overflow trough 2| of the first unit 24 is directed to a second unit 25 whose overiiow trough is in turn directed to a third stage or unit 26. Additional units may be used as desired, the three shown in the drawing being sufiicient to illustrate the principle. With this series of apparatus, each stage of aeration is controlled so that a predetermined drop in density is obtained in each unit. For example,` in the arrangement illustrated inFigure 4, let it be assumed that the initial material entered the first stage 24 from the inlet 21 at a density of 1.125 and thatit is desired that the final material emerging from the last stage 26 have a density of 0.750. The operating conditions are then adjusted so that each stage will decrease the density by 1/3 the difference between 1.125 and 0.750, or 0.125. This is accomplished by adjusting the height of the gate 22 in each unit so that the material begins to discharge from each container when the density in the container has attained a predetermined value. The material then discharges continuously from each container at the predetermined density.

When the run is iirst started, it is necessary to charge the first unit 24, as explained above in connection with the batch process, without introducing any fresh material until the overflow begins at the predetermined density, say 1.000.`

when suflicient material has collected in this unit,

its impeller is started. The overflow from the final stage gives a product having the desired density of 0.750.

This invention can be used to incorporate microscopic air cells in various viscous materials, such as starch paste, proteinaceous materials, synthetic resins, Vinylite resin, and rubber latex.

Having thus described our invention, we claim:

Aerator apparatus comprising a vessel, a circular partition coaxially disposed in said vessel, means for supporting said partition in said vessel above the bottom thereof, the lower section of said partition being imperforate and the upper section comprising a plurality of weirs, said weirs being separated from each other by vertical strips, said strips being narrow'relative to the width of the weirs, said vessel having an overow aperture near the top, a gate adjacent said aperture, and means for securing said gate in different positions relative to said aperture, and means for agitating an impelling iiow of fluid material downward at the bottom of said partition.

ELBERT c. LATHROP. SAMUEL I. ARoNovsKY.

REFERENCES CITED.

The following references are of record in the Certificate of Correction Patent No. 2,461,746. Febrgaryiaggm.

ELBERT C. LATHROP ET AL.

It is hereby certified that errors appear in the printed speoication of the above numbered patent requiring correctlon as follows:

Column l, line 15, for No. 247,699 read No. 2,427,699; column 3, line 42, for 'Wj-'mathe Words or air read of air; v and that thesaidlietters Patent Should begrlad -nwith these corrections therein that the same may conform tothe record of theeasein'the Patent Oiee.

Signed and sealed this 8th day of NovemberLA. 1949. v

THOMAS F. MURPHY,

Assistant Uommz'ss'ioner of Patents. 

